JS determines whether the JSON object and the existence of a field method (recommended) _javascript tips

Examples are as follows:

$.ajax ({
  type: ' POST ',
  Url:url,
  success (function (data) {
    //To determine whether to be a JSON object
    if (typeof (data) = " Object && 
      Object.prototype.toString.call (data). toLowerCase () = = "[Object Object]" &&! Data.length) {
      alert (' is JSON 0bject ');
    }
    Determine if a field
    console.info (datas["key"]!= undefined);//This method is not rigorous, if the key is defined and is assigned a value of undefined will be problematic
    Console.info ("Key" in datas);
    Console.info (Datas.hasownproperty ("key"));

  })

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